The flow of crankcase gases must be controlled, in particular in gasoline turbocharged engines, when it is desired to guide such gases either towards the manifold (for example at low engine load, knowing that there is sufficient negative pressure in the manifold) or towards upstream of the turbocharger, depending on the operative phase of the engine. The management of these flows of clean air and exhaust (“blowby” gases) is driven by the need to always have negative pressure in the crankcase.
More generally, it is understood that it may be necessary to be able to selectively direct the crankcase gases according to the engine load:                either into a first area of the air intake circuit,        or into a second area of the air intake circuit, distinct from the first area.        
It is known to use several valves to do so. In gasoline turbocharged engines in particular, a check valve is used which, in the open state, directs the blowby gases into the area upstream of the turbocharger. In case of insufficient load, the check valve is closed and another valve providing access to the manifold is typically opened (this is a negative pressure circulation mode). At high load, the pressure in the manifold is positive, such that this valve providing access to the manifold is closed, while the check valve opens. The goal is to always have a negative pressure so that the crankcase exerts suction.
On the other hand, a calibrated valve may sometimes be added to limit the suction. It acts to regulate the pressure. For this valve to work properly (under low pressures), it must have a large surface area.
A crowding issue exists in the above systems for controlling the flow of crankcase gases. Indeed, the environment under the cylinder head cover is generally crowded, one or more oil separation devices being placed at this location (devices which may be part of the air intake recirculation circuit). There is therefore a need to integrate effective ways to control the flow of crankcase gases in a highly compact manner.